Preface: I'm well aware of the fact that just because a capacitor looks good that it isn't necessarily good. I'm just giving this a shot anyway. And for the record: no, I do not have a desoldering gun/tool, but probably will invest in a nice Hakko unit after this.
History (all this is on my Twitter if you care): my 13-year-and-counting Dell 2407WFP monitor recently died. Review showed bad caps ("Elite" brand), particularly on the video board, but I found general engineering idiocy on the power board as well. I purchased replacement boards (both video and power), so either way I'll have a working monitor at the end of this.
In the meantime, I decided it would be worthwhile to replace the capacitors on the video board with some quality Nichicon ones. Of the 29 total electrolytic caps on the board:
* 17 smaller caps looked OK -- 47uF 25V
* 7 larger caps were bulging -- (5) 220uF 25V and (2) 220uF 35V
* 5 larger caps looked OK but were physically close to the above 7 and of the same spec, so I decided to replace them -- (3) 220uF 25V, (2) 220uF 35V
This board involved what I believe to be lead-free solder, but of a very weird composition (or maybe just age?), where neither my lead-free nor 60/40 tin/lead solders would "mesh" well with it, which made cap removal difficult. I did the first 7, and despite it taking a few hours, I got them out. Continuity tests were fine (I know this isn't a flawless test, but it's better than nothing), so I was happy.
Then I moved on to the remaining 5 today, which proved to be, for some reason, a bigger pain in the butt than the previous batch. The biggest problem was leftover solder in the hole; no matter what I did solder-wise, the stuff just would not come out. I tried higher temperatures too (785F for example -- yikes), no go. I eventually managed to get them clear by replacing my tip with a substantially "finer" tip and working the hole gently while using a pump on the other side of the board. Picture time, followed by details leading to my question:
https://pbs.twimg.com/media/DpHBZiqU0AAiRMD.jpg:large
https://pbs.twimg.com/media/DpHBYnEVAAEcF9h.jpg:large
What I found a bit peculiar -- and maybe this is important -- was that it was always the negative (-) hole/leg (which are all marked in black on that board) that gave me the most difficulty.
I partially damaged at least one of the pads on the component side -- C34 for sure, and possibly C35:
C34: Part of the (-) pad has been torn off entirely on one side of the board (the side visible in the photos). A continuity test between front and back "kind of" works -- depends on the angle I hold the probe. However, as depicted in the photos, I can't tell where the heck that trace goes. Testing the (-) pad to any other (-) pad on the board works the same as front-and-back; depends on the angle I hold the probe.
C35: Visual inspection of the (-) pad is what makes me wary, but continuity tests (from front to back, and from C35 (-) to C36 (-)) pass fine, so I think that one's probably okay, despite looking ugly.
There are no traces on the back of the board for C34 or C35.
So given the above, and assuming the (-) pad of C34 is shot, how exactly do I work around this properly? I literally cannot tell where that trace goes. Do I lift the (-) leg of the replacement capacitor, and solder a jumper wire from that to... what exactly? The same pad but on the back of the board? Just solder the capacitor (-) leg directly to the (+) pin of FD7 (that's connected to C34 (-), I checked)? I'm unsure given that the trace looks like it "splits".
And yes, I know: if this is a multi-layer PCB, then it's very possible I've damaged things beyond repair and I should just give up now.
History (all this is on my Twitter if you care): my 13-year-and-counting Dell 2407WFP monitor recently died. Review showed bad caps ("Elite" brand), particularly on the video board, but I found general engineering idiocy on the power board as well. I purchased replacement boards (both video and power), so either way I'll have a working monitor at the end of this.
In the meantime, I decided it would be worthwhile to replace the capacitors on the video board with some quality Nichicon ones. Of the 29 total electrolytic caps on the board:
* 17 smaller caps looked OK -- 47uF 25V
* 7 larger caps were bulging -- (5) 220uF 25V and (2) 220uF 35V
* 5 larger caps looked OK but were physically close to the above 7 and of the same spec, so I decided to replace them -- (3) 220uF 25V, (2) 220uF 35V
This board involved what I believe to be lead-free solder, but of a very weird composition (or maybe just age?), where neither my lead-free nor 60/40 tin/lead solders would "mesh" well with it, which made cap removal difficult. I did the first 7, and despite it taking a few hours, I got them out. Continuity tests were fine (I know this isn't a flawless test, but it's better than nothing), so I was happy.
Then I moved on to the remaining 5 today, which proved to be, for some reason, a bigger pain in the butt than the previous batch. The biggest problem was leftover solder in the hole; no matter what I did solder-wise, the stuff just would not come out. I tried higher temperatures too (785F for example -- yikes), no go. I eventually managed to get them clear by replacing my tip with a substantially "finer" tip and working the hole gently while using a pump on the other side of the board. Picture time, followed by details leading to my question:
https://pbs.twimg.com/media/DpHBZiqU0AAiRMD.jpg:large
https://pbs.twimg.com/media/DpHBYnEVAAEcF9h.jpg:large
What I found a bit peculiar -- and maybe this is important -- was that it was always the negative (-) hole/leg (which are all marked in black on that board) that gave me the most difficulty.
I partially damaged at least one of the pads on the component side -- C34 for sure, and possibly C35:
C34: Part of the (-) pad has been torn off entirely on one side of the board (the side visible in the photos). A continuity test between front and back "kind of" works -- depends on the angle I hold the probe. However, as depicted in the photos, I can't tell where the heck that trace goes. Testing the (-) pad to any other (-) pad on the board works the same as front-and-back; depends on the angle I hold the probe.
C35: Visual inspection of the (-) pad is what makes me wary, but continuity tests (from front to back, and from C35 (-) to C36 (-)) pass fine, so I think that one's probably okay, despite looking ugly.
There are no traces on the back of the board for C34 or C35.
So given the above, and assuming the (-) pad of C34 is shot, how exactly do I work around this properly? I literally cannot tell where that trace goes. Do I lift the (-) leg of the replacement capacitor, and solder a jumper wire from that to... what exactly? The same pad but on the back of the board? Just solder the capacitor (-) leg directly to the (+) pin of FD7 (that's connected to C34 (-), I checked)? I'm unsure given that the trace looks like it "splits".
And yes, I know: if this is a multi-layer PCB, then it's very possible I've damaged things beyond repair and I should just give up now.